linux-kernel - Re: [PATCH v2 1/3] overflow.h: Add arithmetic shift helper

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Message-ID: <20180801021508.GB31192@ziepe.ca>
Date:   Tue, 31 Jul 2018 20:15:08 -0600
From:   Jason Gunthorpe <jgg@...pe.ca>
To:     Kees Cook <keescook@...omium.org>
Cc:     Rasmus Villemoes <linux@...musvillemoes.dk>,
        Leon Romanovsky <leonro@...lanox.com>,
        Leon Romanovsky <leon@...nel.org>,
        Bart Van Assche <Bart.VanAssche@....com>,
        Doug Ledford <dledford@...hat.com>,
        Dan Carpenter <dan.carpenter@...cle.com>,
        linux-rdma@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/3] overflow.h: Add arithmetic shift helper

On Tue, Jul 31, 2018 at 05:00:37PM -0700, Kees Cook wrote:
> From: Jason Gunthorpe <jgg@...lanox.com>
> 
> Add shift_overflow() helper to assist driver authors in ensuring that
> shift operations don't cause overflows or other odd conditions.
> 
> Signed-off-by: Jason Gunthorpe <jgg@...lanox.com>
> Signed-off-by: Leon Romanovsky <leonro@...lanox.com>
> [kees: tweaked comments and commit log, dropped unneeded assignment]
> Signed-off-by: Kees Cook <keescook@...omium.org>
> ---
>  include/linux/overflow.h | 31 +++++++++++++++++++++++++++++++
>  1 file changed, 31 insertions(+)
> 
> diff --git a/include/linux/overflow.h b/include/linux/overflow.h
> index 8712ff70995f..69fc366ce865 100644
> --- a/include/linux/overflow.h
> +++ b/include/linux/overflow.h
> @@ -202,6 +202,37 @@
>  
>  #endif /* COMPILER_HAS_GENERIC_BUILTIN_OVERFLOW */
>  
> +/** check_shift_overflow() - Calculate a left-shifted value and check overflow
> + *
> + * @a: Value to be shifted
> + * @b: How many bits left to shift

The above @b should be @s

> +#define check_shift_overflow(a, s, d) ({				\

Should I run this series through the rdma tree?

Thanks,
Jason